Products from refineries such as gasoline, diesel etc. are produced by blending various component streams in order to meet product specifications. For example, gasoline blend is produced in a refinery by blending streams such as reformate, alkylate, FCC naphtha (fluid catalytic cracking naphtha), straight run naphtha, ethanol, TAME (tertiary amyl methyl ether), etc. Gasoline production is constrained by property specifications such as RON (research octane number), MON (motor octane number), RVP (reid vapor pressure), density, distillation, sulfur, aromatics, olefins, benzene and the like. Each of these component streams have different properties and are blended in various proportions to meet gasoline specifications.
These component streams have minor to large property fluctuations on a day to day basis. Based on the component stream property values, the blend proportions are altered to meet the specifications. Experimental techniques and tests for analysis of gasoline include RON/MON by CFR (co-operative fuel research) engine test (ASTM D2700, EN 25163, IP 236, ASTM D2699, EN 25164, IP 237), distillation by ASTM D86, RVP by ASTM D323, API/density by ASTM D-287, D-1298, sulfur content by X-Ray ASTM D-4294/D-2622, benzene and total aromatics by D3606, D5769, D5580, aromatics/olefins by ASTM D-1319, mercaptan sulfur by D-3227 etc. For diesel, these techniques include cetane number ASTM D-613, IP 41, EN ISO 5165, distillation by ASTM D86, cetane index by ASTM D-4737, IP 380, EN 4264, ASTM D-976, API/density by ASTM D-287, D-1298, flash point measurements, cloud point/cold filter plugging point measurements, sulfur by ASTM D2784, D3246, D3961, D4468, D6212, D6667, D5453, D7039, (EDXRF) ASTM D4294 etc.
The production of gasoline blend involves component streams in various proportions. Optimizing said proportions to maintain the product quality and to meet the gasoline specifications is very much necessary to avoid tank failures and to reduce demurrage of product tank. Optimization of the gasoline blend is conducted by analyzing the gasoline blend and said analysis is generally performed by using conventional techniques. Analysis of such gasoline blend involves the following steps: collecting liquid sample from the product tank, analysis of said sample, determining the proportions of component streams, optimizing said proportions to meet gasoline product specifications and controlling flow of the component streams to produce standardized gasoline blend product.
However, these approaches of analysis of gasoline blend encounter many drawbacks. Firstly, the above mentioned processes for analysis of the gasoline blend are time consuming. This makes it practically impossible to analyze gasoline blend in a short period of time and maintain the required product tank specification. During the time which is required for analysis and optimization of the gasoline blend, there are threats of tank failure, quality give away, loss of valuable streams, demurrage and the like.
Hydrocarbon product tanks, particularly gasoline/diesel product tanks are analyzed and certified before shipments. Analysis of a product tank is generally carried out based on the requirement of a product specification. For the above purpose, tank samples are analyzed by various common lab tests which include research octane number (RON)/motor octane number (MON) by co-operative fuel research (CFR) engine test, distillation by ASTM D86, reid vapor pressure (RVP) by ASTM D323, density by ASTM D1298-99, cetane number, cetane index, cloud point, cold filter plugging point, flash point etc. Conducting all these lab tests of samples from the product tank are time consuming and depend on laboratory facilities and the product specification. Furthermore, filling the product tank for shipment requires one/two days. Due to this reason, the product tank analysis is generally performed only once before shipment, which results in changes in the properties of hydrocarbons in the product tank. Such changes in the properties of hydrocarbons in the product tank affects the product tank which does not meet the desired specification, thus the product tank failures, quality give away and demurrage of the product tank and the like occur.
U.S. Pat. No. 6,966,326 provides a method for analyzing hydrocarbon liquids which are withdrawn from pipelines. Analysis and withdrawal of said hydrocarbon liquid is controlled by a system, wherein said system includes intercommunicating analyzers, control applications and controllers for analyzing and controlling the flow of a liquid from a pipeline system. Said system involves an analyzer which is a gas chromatography device.
GB1419655 discloses an apparatus for continuously monitoring gasoline blending operations, said apparatus comprising an analyzer, a detector, a multiplier and an uptown counter incorporating a visual display device. The apparatus particularly monitors the continuous blending operation of gasoline fluid to obtain a blended gasoline of the desired octane ratings.
GB1170616 provides an apparatus for maintaining the ratio between two flowing media, particularly for controlling the blending of gasoline and butane to provide gasoline with the desired volatility. The apparatus mentioned in this patent comprises: a ratio controller, a circuit for deriving a voltage from the control variable, and a resistance coupled between the circuit and the reservoir capacitor of the controller.
U.S. Pat. No. 3,751,644 provides a system for automatically adjusting proportions of given streams to form a gasoline blended product. The automatic system maintains the RVP and the octane number of the blended streams at particular pre-determined values.
U.S. Pat. No. 3,672,840 discloses a method and an apparatus for continuously determining and controlling a composition characteristic of the combustible fluid mixture wherein said composition characteristic is octane rating and said combustible fluid mixture is a gasoline blend.
JP5163493 discloses a method to obtain a gasoline product, said method includes controlling research octane value (ROV), density and vapor pressure of a mixture containing gasoline, reformate, light naphtha and butane; analysis of gasoline by using gas chromatography; and adjusting proportions of blended components based on analysis to give a gasoline having the desired octane value, density and vapor pressure.
Prior art lacks a system and a method which can carry out a quick and efficient analysis of a gasoline blend thereby optimizing blending proportions of the component streams to meet a standardized product specification. There is thus felt a need for a technique which can quickly analyze and optimize the gasoline blend and meet the gasoline product specification. By using said technique, analysis of the gasoline blend is performed outside a product tank and the proportions of component streams are optimized, thereby controlling the flow of the component streams for the production of a desired hydrocarbon blend.